Fuse



July 24, 1934.

R. L. SMYTHE FUSE Filed Jan. 27, 1932 2 Sheets-Sheet l R. L. SMYTHE July 24, 1934.

FUSE

Filed Jan. 27, 1932 2 Sheets-Sheet 2 MW w M Fm .f m v Patented July 24, 1934 UNITED STATES PATENT OFFICE FUSE Robert L. Smythe, Milwaukee, Wis., assignor to 3;:

Line Material Company, South Milwaukee, Wis., a corporation of Delaware Application January 27, 1932, Serial No. 589,175

6 Claims. (01. 200-117) 517 This invention relates to fuses and is particularly directed to a liquid fuse.

In liquid fuses as heretofore constructed, it is the usual practice to provide a spring for tensioning the fuse link and for pulling the fuse link down into the liquid when fusing occurs. This construction is not wholly satisfactory as heretofore practiced in small amperage fuses for the reason that under the spring'tension it is 10 very difficult to get a fuse wire which will satiswith low amperage fuses.

This invention is designed to overcome the defects noted above, and objects of this invention are to provide a novel form of fuse, preferably of the liquid fuse type, which is so constructed that although a spring is used to retract a portion of the fuse structure below the liquid level, that neverthelessonly a relatively small tension, or substantially no tensionat all, is placed upon the fuse link, although as powerful a springmay 5 be employed as desired, the initial pull of the springbeing borne by thestructure of the liquid fuse and not directly borne by the fuse link itself, thereby enabling a fuse link to be employed which may be as small as desired as there no danger of mechanically pulling the fuse in two due to the action of the spring.

Further objects are to provide a liquid fuse having the characteristics noted above which nevertheless is so constructed that the spring re- 5 tracts a portion of the fuse structure below the and is so constructed that the motion of the retaining member is prevented by the fuse link, the parts being so organized that when the fuse link ruptures, the retaining member may move to a disengaging position and allow the spring and its associated parts to quickly move downwardly into the arc extinguishing liquid, thereby retaining all of the heretofore known advantages of liquid type fuses while at the same time permitting the use of any type of fuse link desired, no matter for what amperage the link may be constructed, or, in other words, irrespective of the frailty of the link itself.

The invention contemplates the use of standard liquid fuse construction for the major portion of M the apparatus and enables the use of the novel 6 portions thereof with this standard construction, thereby greatly cheapening the cost of production and adhering, so far as manufacture is concerned, fairly close to the original types of construction now universally employed, and in certain forms the invention contemplatesthe use of adjustable means to adjust the position of the spring retaining member or latch and the use of a guard to prevent portions of the fuse structure from being blown bodily from the device.

Embodiments of the invention are shown in the accompanying drawings, in which:-

Figure 1 is a side elevation, partly in section and partly broken away, showing one form of the invention.

Figure 2. is a transverse sectional, view .on the line2- -2 of Figurel. e Q

Figure 3 is a vertical sectional view of a further form of the invention. v Figure 4 is a transverse sectional view on the line 44 of Figure 3. H

Figure 5 is a sectional view of a further form of the. invention.

Figure 6 is a transverse sectional view on the line 6--6 of Figure. 5.

Figure '7 is a sectional view of a further form of the invention.

Referring to Figures 1 and 2, it will be seen that the liquid fuse comprises a main body portion or tube 1 of insulating material, such as glass, and adapted to contain an arc extinguishing liquid in theusual manner. This glass tube 1 is provided with an upper, contact member 2 and a lower contact member .3 in the usual manner.

Within the body portion or tube 1 a spring 4 and a flexible leader 5 are anchored to the lower contact 3 in the usualmanner, not shown. The upper end of the spring hooks into the lower portion of a fitting Gito which the leader 5is also attached in any suitable manner, as by means of the screw'7'. q

The construction is such that both the leader and the spring may be detached from the fitting 6 if desired so that a new fitting can be used if the original fitting becomes injured in use, requiring onlya very small amount of work to make this substitution. g

The upper contact 2 is an annular member and is provided with a shoulder upon which an inhis ids

i i-b sulating bearing ring '7 rests, such ring being provided with semi-cylindrical grooves 8 at diametrically opposite points, as shown in Figure 2, to receive a fiber or insulating pintle pin 9. The pintle pin 9 carries a latch member which is provided with an upstanding arm 10 and a lower laterally extending arm 11, the arms constituting in effect a bell crank lever, as shown in Figure 1. Normally the arm 11 rests upon the ring "7, as shown in Figure 1. The arm 10 is provided with an attaching member, such as the screw 12, whereby the end of a fuse link 13 may be secured to the upper end of the arm 10. The other end of the fuse link 13 is clamped to a shouldered projecting portion 14 formed on the contact '2 by means of the screw 15. Obviously, other fastening means could be employed in place of the screws 12 and 15 without departing from the spirit of this invention.

The latch or retaining member is provided with a shouldered face 16 which receives the upper portion of the fitting 6, such upper portion constitu inga hook or similar member and being provided with a transversely extending bar or portion 17 which rests upon the shouldered portion 16 of the hook, as shown in Figures 1 and 2.

This bar or transverse member 17 is connected to the body portion 6 of the fitting by means of the spaced arms 18 so as to leave an open space within which the hub portion of the retaining member may be freely received, as shown most clearly in Figure 2.

The upper end of the fuse may be covered by a leadior other washer or rupturable diaphragm 19 held in place by means of an annular nut 20.

Thetension, of the spring 4-is imparted directly to the hook, but this hook rests upon the face 16 of the latch or retaining member, and it is to be noted from Figure 1 that the center line of the member 1'7 is slightly offset from the center line .of the pintle pin or supporting member 9 so that there is a slight tendency to rock which is imparted to the latch. or retaining member. This rocking tendency of the latch it restrained by means of the fuse link 13, the fuse link'bemg, however, only slightly tensioned although the pull of the spring 4 may be relatively great.

When fusing occurs, the fuse link 13 is ruptured and the arm 10 rocks in a clockwise direction, as viewed in Figure 1, thereby releasing the hook and allowing the spring to retract the hook downwardly into the body portion or tube 1 and into the arc extinguishing liquid, thereby causing a very wide separation of the active parts of the fuse structure and quickly extinguishing any are that may be formed. In the form of the invention shown in Figures 3 and4 substantially the same idea is followed but a slightly different structure is employed. In this form of the invention the upper contact member '21 is relatively elongated and an insulating ring22 rests upon the shouldered portion and is provided with an inwardly projecting lip 23 to whichea normally vertically extending arm or hook member 24 is pivoted. This hook member is provided with a slot 24' which receivesthe hook or bail 25, such hook or bail being attached to a fitting 26 secured to the spring 27 and to the flexible leader'28. The member 25 may take the form of a looped wire which normally is positioned on Opposite sides of a portion of the projecting lip 23, but which rocks clear of the lip 23 when the arm 24 rocks into its dotted line position shown in-Figure 3. The upper end of the arm 24 has one end of a fuse wire or fuse link 29 secured thereto in any suitable manner, either as previously described or else as shown in Figure 3 by looping the fuse link around a notched portion of the arm and twisting the fuse link upon itself.

The other end of the fuse link is secured to a projecting portion 33 formed integrally with the upper contact 21 by means of .a screw 31, as shown in Figure 3. The operation of this form of the invention is the same as that previously described in connection with Figure 1, it being noted that there is a slight initial tendency for the member 24 to rock due to the fact that the center line of the member 21 is slightly off center with reference to the center lineof the pintle pin 32 which pivotally supports the member 24.

In the form of theinvention shown in Figure 5 the upper contact 33 carries a metal ring 34 which is provided with spaced lugs 35, see Figure 6,

which carry a bakelite or insulating pintle pin 36.

This pintle pin supports the retaining member, as in the forms previously described, and the retaining member in this form of the invention com prises the upstanding arm 37 and a laterally extending arm 33. It is also provided with a shouldered portion 39 which receives the transverse portion 40: of the hook, the lower portion of the hook, indicated at 41, being attached to the spring 42 and the flexible leader 43 in any suitable manner, for example as previously described in connection with Figure 1. However, the hook is provided with an apertured ear 44 which facilitates the repositioning of the hook as the apertured ear may be engaged by a suitable tool projected down into the tubular body portion 1 and may thereby be drawn upwardly f01 reengagement;

with the retaining member.

The metal ring 34 is provided with an upwardly extending arm 45 which is joined integrally to the ring by means of an oifset portion through which an adjusting insulatingscrew, of fiber or similar material 46 is threaded. This screw bears against the arm 38 of the latch or retaining member, see :Figure 5, and thus may be used to adjust the position of such retaining member.

; The upper end of thearm 3'7 is joined to the 1 upper end ofthe arm 45 by means of thefuse link 47..

A protecting means may be employed for guardingagainst the outward flying of any por tions of the mechanism, and this protecting 1 means may be employed with any form of the invention. It is, howevenshown in Figure 5 and consists of a perforated metal disc 48, the'perfo rations being preferably relatively large and being indicated by the reference character 49 in Figure 5. This disc is placed upon a lead washer or similar member or disc 50, and is preferably covered by a metal disc, such as the tin disc 51, althoughobviously this exact construction may be varied as desired provided a suitable seal isob- 1' tained.

Thediscs andthe perforated member are retained in place by means of the annular nut 52'. The portion of this form of the invention will be readilyunderstood from the previous de'scrip parting from the spirit thereof.

oom 3 spring is concerned. Before entering into a de-.

tailed description of this form of the invention, it

is tobe .distinctly understood that this principle may be applied to any form of the invention, and also'that principles of one form of the invention may be appliedto that shown inany other form Without. departing from the spirit of the inven tion, the detailed description and'drawings'being illustrative of a few of the forms that the invention-may take.

Referring in detail to Figure 7, it will be seen that the upper contact member 53 is provided with a shouldered portion upon which an insulating ring 54 rests, such ring carrying an insulating pintlepin 55. This pintle pin supports the latch member 56, and the latch member may consist of a platelike or fiat body portion provided with a lower tongue or hook 5'? which is normally positioned within "the aperture 58 of the fitting 59, such latter member being attached to the spring 60 and to the flexible leader 61. The upper portion of the latch 56 is provided with a pair of apertures 62 and 63, and it is to be noted also that the upper portion of the upper contact 53 is provided with an additional shouldered portion indicated at 64, upon which a metal ring 65 rests. This ring 65 is preferably provided with a beveled upper face, as shown in Figure '7. One end of a fuse link 66 is passed through the aperture 62 and twisted upon itself or otherwise secured to the member 56. Its other end is clamped to the ring 65 by means of the screw or other suitable member B7. A spring 68 located diametrically opposite the link 66 has one end secured by 1 means of a screw 69 to the ring, and its other end passed through the aperture 63 in the member 56. However, it is to be noted that the spring 68 does not electrically connect the ring 65 and the member 56. Any suitable means may be employed for insulating the spring from the member 56 so that all of the current passing through the contact 53 to the member 56 will be forced to pass through the link 66. For example, the aperture 63 may be provided with an insulating bushing '70, or other means may be employed to accomplish this same result.

The operation of this form of the invention is very similar to that previously described. However, the only tension imposed upon the fuse link 66 is that due to the action of the spring 68 and is not due to the main spring 60, although a combination of these two tensions may be imparted to the link 66 by slightly altering the design if so desired. However, this form of the invention shows an auxiliary spring 68 which imparts the initial rocking motion to the hook or latch 56 when the link 66 is ruptured by overload.

When the latch 56 is rocked, the tongue 5'7 disengages the member 59 and the spring 60 retracts such member downwardly beneath the are extinguishing liquid, as previously described.

As stated, it is clear that the auxiliary spring 68 or its equivalent could be employed in any of the several forms of the invention without de- This use of the auxiliary spring could be employed whether the main spring tended to rock the hook or retaining member or not, depending, of course, upon the exact relation of the center of the supporting pin and the point of application of the force due to the main spring. Clearly the construction could be varied to obtain whatever resuit was desired and still remain within the spirit 1 of this invention.

It' will be seen-that, anovel form of fuse construction has been shown'which although applicable to larger sizes of fuse links, is nevertheless particularly suited for small rating ,fuse. links.

Further, it will be seen that any suitableten-- J sion may be employed for the'main spring'and yet the actual tension imposed upon the fuse link may be very small indeed, and thus afragile or delicate, small current carrying capacity fuse link can be employed with this. invention with the assurance that it will not be mechanically ruptured.

It will be seen further that the invention is eminently practical, and-that the device is relatively easy to construct and may be cheaply made.

Although this invention has been described" in considerable'detail, it is to be understood that such description is intended as illustrative rather than limiting, as the invention may be variously embodied and is to be interpreted as claimed.

I claim:

1. A liquid fuse comprising a tubular body portion adapted to contain an arc extinguishing liquid and having upper and lower contacts, a latch pivotally supported from said upper contact and having a supporting arm normally held in an approximately vertical line through said pivot point, a fuse link electrically connected to said upper contact and to said latch, and tensioned contractible means normally held by the supporting arm of said latch and tending to draw downwardly from said latch and normally electrically connecting said latch and said lower contact, said means being released from said latch when said fuse link is ruptured, said latch in normal position exerting the minimum stress upon said fuse link.

2. A liquid fuse comprising a tubular body portion adapted to contain an arc extinguishing liquid and having upper and lower contacts, a single latch supported from said upper contact, a fuse link electrically connected to said upper contact and to said latch, said latch being in the form of a lever and having a pivot point, and tensioned contractible means normally held by said latch and tending to draw downwardly from said latch and normally electrically connected to said latch and said lower contact, said means being released from said latch when said fuse link is ruptured, the line of pull of said tensioned means being adjacent said pivot point, said latch relieving said fuse link of the major portion at least of the tension of said contractible means, said latch in normal position exerting the minimum stress upon said fuse link.

3. A liquid fuse comprising a tubular body portion adapted to contain an arc extinguishing liquid and having an upper and lower contact, a latch supported from said upper contact, a conducting member releasably and directly held by said latch and electrically connected to said lower contact, a spring tending to draw said conducting member towards said lower contact, and a fuse link electrically and directly connecting said latch and said upper contact and nor- I40 mally holding said latch from moving to releasing position, the pull of the spring being directly borne by said latch, said latch in normal position exerting the minimum stress upon said fuse tact, a fuse link electrically connecting said latch and' said upper contact and normally holding said latch against rocking motion, and a conducting member engaging said latch and held by said latch, said conducting member being electrically connected to said lower contact, said latch being urged towards releasing position and said conducting member being urged in a direction away from said latch, said pivoted latch being normally held in a position closely adjacent dead center, whereby the minimum stress is imposed'upon said fuse link.

5. A fuse comprising a body portion having upper and lower contacts, a lever pivotally supported from said upper contact and having two arms, one of said arms being mechanically normally restrained from movement by a fuse link and being electrically connected by said fuse link to said upper contact, the other arm of said lever being on approximate dead center, movable means releasably supported by said last mentioned arm and electrically connected to said lower contact, and a spring tending to draw said means downwardly.

6. A fuse comprising a body portion having two spaced contacts, a lever having a long arm and a short arm and pivotally supported from one of said contacts, a fuse link mechanically restraining the long arm of said lever from motion and electrically connected to said last mentioned contact and to said long arm, a movable member bearing against said short arm and electrically connected to the other contact, and a spring tending to draw said member towards said last mentioned contact, the line of pull of said arm and the pivot point of said lever.

ROBERT L. SMYTHE. 

